Achieving　nitrite　accumulation　was　considered　as　the　prerequisite　of　ANAMMOX,　which　hindered　the　application　of　ANAMMOX.　In　this　study,　total　inorganic　nitrogen　(TIN)　removal　during　the　partial/complete　nitrification　was　studied　in　a　lab-scale　sequencing　batch　reactor　(SBR)　for　treating　domestic　wastewater.　The　results　showed　TIN　was　removed　by　denitrification,　ANAMMOX　and　N2O　emission　during　the　partial/complete　nitrification.　AOB,　AOA,　Nitrobacter　(NB),　Nitrospira　(NS),　AnAOB　and　DNB　were　coexisted　in　the　partial/complete　nitrification.　The　microbial　competition　among　these　functional　communities　determined　the　type　of　nitrification,　TIN　removal　and　pathways.　Since　low　DO　concentrations　benefits　Nitrospira　growth,　the　partial　nitrification　was　damaged.　After　long-term　operation,　AOB　gradually　accommodated　the　low　DO　concentration.　When　V-max,V-AOB　(the　maximum　specific　reaction　rate　of　AOB)　higher　than　Vmax,　NOB　(the　maximum　specific　reaction　rate　of　NOB),　a　part　of　nitrite　was　reduced　by　DNB　and　AnAOB.　Therefore,　TIN　was　removed　during　the　complete　nitrification.